Project 2 is a new project that has developed from the Career Development Program of the UAB SPORE in Breast Cancer. The PI initially developed a novel anti-DR5 monoclonal antibody, TRA-8, which exhibited a strong apoptosis-inducing activity against cancer cells without hepatocyte cytotoxicity. With the support of the Career Development funds and in collaboration with our industrial sponsor, Sankyo Co, Ltd, TRA-8 has been explored in pre-clinical studies and has moved into development as an anti-cancer candidate. The overall goal of this proposal for the competitive renewal is to develop an effective therapeutic strategy for treatment of breast cancer by selectively targeting DR5 with a novel monoclonal TRA-8 in combination with chemotherapy. The central hypothesis is that breast and other cancer cells may differentially express increasing levels of DR5 during malignant transformation and that DR5 can be selectively targeted with an agonistic monoclonal antibody to directly induce apoptosis of cancer cells. As TRA-8 and chemotherapy agents may utilize different but complementary pathways to trigger apoptosis, the susceptibility of breast cancer cells to TRA-8-mediated apoptosis can be enhanced by chemotherapy agents. Furthermore, TRA-8 may improve the efficacy of chemotherapy by preventing or reversing chemo-resistance in breast cancer cells. There are four Specific Aims: Aim 1 is to examine the efficacy of TRA-8 (anti-DR5) with and without chemotherapy agents in murine models of orthotopic and metastatic human breast cancer; Aim 2 is to characterize the role of the DR5/DDX3 pathway in modulating sensitivity or resistance of breast cancer cell lines to TRA-8 induction of apoptosis, and to characterize the DR5/DDX3 pathway in human breast cancer tissue samples; Aim 3 is to determine in vitro and in vivo synergistic mechanisms of combination therapy with TRA-8 and chemotherapy; Aim 4 is to initiate clinical development of CS-1008 (humanized TRA-8) in breast cancer. The proposed basic and translational studies will support the proposed clinical studies. Accomplishment of these studies will yield a new and potentially effective therapy for breast cancer. The goal of this research is to evaluate a new antibody for the treatment of breast cancer. The research will identify the mechanisms for maximizing the efficacy of the antibody in combination with chemotherapy and the development of biomarkers for predicting the response of patients in clinical trials.